Impact of climate change and other factors on emerging arbovirus diseases

While some skeptics remain unconvinced that global climate change is a reality, there is no doubt that during the past 50 years or so, patterns of emerging arbovirus diseases have changed significantly. Can this be attributed to climate change? Climate is a major factor in determining: (1) the geographic and temporal distribution of arthropods; (2) characteristics of arthropod life cycles; (3) dispersal patterns of associated arboviruses; (4) the evolution of arboviruses; and (5) the efficiency with which they are transmitted from arthropods to vertebrate hosts. Thus, under the influence of increasing temperatures and rainfall through warming of the oceans, and alteration of the natural cycles that stabilise climate, one is inevitably drawn to the conclusion that arboviruses will continue to emerge in new regions. For example, we cannot ignore the unexpected but successful establishment of chikungunya fever in northern Italy, the sudden appearance of West Nile virus in North America, the increasing frequency of Rift Valley fever epidemics in the Arabian Peninsula, and very recently, the emergence of Bluetongue virus in northern Europe. In this brief review we ask the question, are these diseases emerging because of climate change or do other factors play an equal or even more important role in their emergence?     

Arbovirus prevalence in mosquitoes, Kenya

Few studies have investigated the many mosquito species that harbor arboviruses in Kenya. During the 2006-2007 Rift Valley fever outbreak in North Eastern Province, Kenya, exophilic mosquitoes were collected from homesteads within 2 affected areas: Gumarey (rural) and Sogan-Godud (urban). Mosquitoes (n = 920) were pooled by trap location and tested for Rift Valley fever virus and West Nile virus. The most common mosquitoes trapped belonged to the genus Culex (75%). Of 105 mosquito pools tested, 22% were positive for Rift Valley fever virus, 18% were positive for West Nile virus, and 3% were positive for both. Estimated mosquito minimum infection rates did not differ between locations. Our data demonstrate the local abundance of mosquitoes that could propagate arboviral infections in Kenya and the high prevalence of vector arbovirus positivity during a Rift Valley fever outbreak.     

Chikungunya fever as a risk factor for endemic Burkitt's lymphoma in Malawi

The geographical and age distributions of endemic Burkitt's lymphoma (eBL), in Africa, parallel those of certain arboviruses, which include chikungunya fever. Increased incidences of antibodies to assorted arboviruses, including chikungunya, have been found in eBL sera compared to controls. An increased incidence and space-time case-clusters of eBL occurred during a chikungunya fever epidemic which were confirmed by serology and clinical observation. The present study, conducted in 1987-89, involved 108 eBL patients, and 97 local and 111 hospital controls. We examined, as hospital controls, patients with afebrile, non-malignant conditions admitted to Kamuzu Central Hospital, Malawi, during the eBL patients' first admission there. Analyses were for hospital controls and eBL patients at the end of their first admission and for local controls and eBL patients at the beginning of their third admission, about 8 weeks after the day of first admission, because of the local controls' temporal bias. Patients in case-clusters were among those seropositive for chikungunya virus, with a history compatible with arbovirus infection preceding the lymphoma, suggesting involvement of chikungunya virus in the case-clusters and a possible association between recent infection with this virus and development of the lymphoma. eBL patients were significantly more likely to be seropositive for chikungunya virus antibody (68x5%) than either hospital controls (46.8%) or local controls (50x5%) (P = 0x002 and 0x009, respectively), raising the possibility of an association between infection with an arbovirus and developing eBL in children already primed by holoendemic malaria and Epstein-Barr virus infection.     

云南省西双版纳地区2011年蚊虫及虫媒病毒调查

目的了解云南省西双版纳地区蚊虫媒介的分布特点及当地虫媒病毒情况,为虫媒病毒病防治提供科学依据。方法在云南省西双版纳州采集蚊虫标本,用细胞培养法分离病毒,并用RTPCR法检测常见虫媒病毒核酸;在西双版纳州采集发热患者血清及脑脊液标本,并用ELISA法检测常见病毒性脑炎IgM抗体。结果共采获蚊虫5属29种13337只,其中三带喙库蚊、中华按蚊、带足按蚊分别占蚊虫标本总数的79.98%(10667/13337)、7.95%(1060/13337)和7.38%(984/13337),三带喙库蚊为当地优势蚊种。采用流行性乙型脑炎(乙脑)病毒、版纳病毒、甲病毒属、环状病毒等多种虫媒病毒引物对214批蚊虫标本进行PCR检测,结果均为阴性;采用多种细胞对蚊虫标本进行病毒分离,结果也为阴性。用相关脑炎病毒试剂盒对采集到的52份急性期血清标本及54份脑脊液标本进行ELISA检测,发现乙脑病毒IgM阳性16例,单纯疱疹病毒IgM抗体阳性4例,腮腺炎病毒IgM抗体阳性13例,埃可病毒IgM抗体阳性3例,登革热病毒IgM抗体阳性1例。结论 2011年西双版纳地区采集到的蚊虫标本中未检测到乙脑、版纳及环状病毒等虫媒病毒,但血清学检测结果表明当地发热患者存在乙脑等多种病毒性脑炎感染。     

内蒙古自治区采集的蚊虫标本新发现乙脑病毒和盖塔病毒

目的 了解内蒙古自治区的吸血昆虫及其携带虫媒病毒的种类及分布,为虫媒病毒病的预防提供基础数据。方法 在自然界使用灯诱法采集蚊虫标本,形态学分类后分装编号,液氮保存。组织培养法进行病毒分离。使用多种生物学信息软件(BioEdit、MEGA等)对病毒核苷酸序列进行分子生物学特征分析。结果 2014、2017-2018年在内蒙古自治区5个县(旗)的采集点共采集到2属3种蚊虫24 240只,蠓虫17 110只。其中在淡色库蚊标本中检测到乙脑病毒基因阳性,并且获得4株可以稳定传代的病毒分离物,经分子生物学鉴定分别为盖塔病毒、浓核病毒。盖塔病毒(NMDK1813-1)E2基因遗传进化分析结果显示,与甘肃分离株(GS10-2)在同一进化分支,且有6个共同的氨基酸变异位点。结论 本研究发现的乙脑病毒和盖塔病毒均是在内蒙古蚊虫标本中新近发现的病毒,这为内蒙古地区的虫媒病毒及其传播疾病的预防及控制提供了基础数据,对内蒙古的虫媒病毒及其病毒病的预防及控制提出了新的挑战。     

Factors contributing to and strategies to combat emerging arboviruses

ABSTRACT

Less than half a century ago infectious diseases appeared to be destined to be extinguished via as a culmination of medical triumphs. As focus turned towards combating non-communicable diseases, emerging and re-emerging diseases (EIDs) have bloomed from those ashes. Five epidemic mosquito-borne arboviruses (Yellow Fever virus (YFV), Dengue virus, West Nile virus, Chikungunya virus, and Zika virus) have emerged in the recent past. Arboviruses are of the utmost importance with respect to EIDs due to intensive growth of globalisation, arthropod urban fitness/adaption, and environmental changes. We focus on recent outbreaks of the arthropod borne viruses (arboviruses) Zika virus and YFV. Factors contributing to the blossoming of EIDs (environmental, globalisation, and urbanisation) and combating strategies (surveillance, containment, and prevention) will be discussed. Specifically, Zika virus and YFV will be used in the context of these factors and strategies. YFV is discussed in detail as it pertains to these factors and strategies in the United States (US), 2017 Brazil Outbreak, 2016 Africa Outbreak, and global risk. Vigilance is needed to focus on, prevent, and control the current and next arbovirus EIDs.     

Arboviruses in the Astrakhan region of Russia for 2018 season: The development of multiplex PCR assays and analysis of mosquitoes,ticks, and human blood sera

The Astrakhan region of Russia is endemic for the number of arboviruses. In this paper, we describe the results of the detection of the list of neglected arboviruses in the Astrakhan region for the 2018 season. For the purpose of the study in-house PCR assays for detection of 18 arboviruses have been developed and validated using arboviruses obtained from Russian State Collection of Viruses. Pools of ticks (n = 463) and mosquitoes (n = 312) as well as 420 samples of human patients sera have been collected and analyzed. Using developed multiplex real-time PCR assays we were able to detect RNA of eight arboviruses (Crimean-Congo hemorrhagic fever virus, Dhori (Batken strain) virus, Batai virus, Tahyna virus, Uukuniemi virus, Inkoo virus, Sindbis virus and West Nile fever virus). All discovered viruses are capable of infecting humans causing fever and in some cases severe forms with hemorrhagic or neurologic symptoms. From PCR-positive samples, we were able to recover one isolate each of Dhori (Batken strain) virus and Crimean-Congo hemorrhagic fever virus which were further characterized by next-generation sequencing. The genomic sequences of identified Dhori (Batken strain) virus strain represent the most complete genome of Batken virus strain among previously reported.     

Fièvre jaune,dengue, encéphalite japonaise et virose West Nile, 4 arboviroses majeures

Yellow fever, Dengue, Japanese encephalitis, and West Nile virus infection are induced by 4 strongly epidemic major arboviruses. Despite its vaccine, yellow fever remains very active in tropical Africa and in South America. The insufficient immunization coverage and population mobility explain the permanence of the epidemics. Vaccination is essential for travelers going to endemic regions. The prevalence of dengue has increased considerably in the last decades. The number of countries concerned with its hemorrhagic forms is also increasing. It is the most frequently observed arbovirus disease in travelers. Widespread in Asia, Japanese encephalitis can be prevented by a specific vaccination. The development of tourism to endemic areas raises the issue of risks for travelers and what preventive measures may be available. The West Nile virus has been present in North America since 1999. There, it caused the most severe epidemic ever observed, in the summer 2002. The clinical expression of the disease has changed over the last 10 years. Initially regarded as a benign virus, it is now considered as being able to cause neurological forms with a high death rate, particularly in elderly people.     

Arbovirus surveillance in Rhode Island: assessing potential ecologic and climatic correlates

During 1995-2000, mosquitoes were collected from sites throughout Rhode Island and tested for the presence of arboviruses. Mosquito trapping was done weekly from June to October with CO2-baited light traps. In all, 186,537 mosquitoes belonging to 7 different genera were collected, of which Coquillettidia perturbans was most abundant. A total of 6,434 pools were processed for arbovirus isolation, from which 193 arboviral isolations were made. These included 109 Highlands J, 71 eastern equine encephalomyelitis, 1 California encephalitis serogroup, 2 Jamestown Canyon, 3 Cache Valley, and 9 Flanders viruses. Our isolations of Flanders virus represent the 1st reported occurrence of this virus in Rhode Island. After the 1999 sudden occurrence of the West Nile virus (WN) in the New York City area, a dead-bird surveillance program was started to test for this virus. Although no isolations of WN were made from mosquitoes, 87 virus isolations were made from a total of 330 wild birds tested. All the WN-infected birds were either American crows or blue jays. Isolation of WN from dead birds marked the 1st documented appearance of this virus in Rhode Island. Significant interannual variation of arbovirus activity in Rhode Island prompted us to examine if climate-associated factors such as rainfall and temperature correlate with virus activity. Total rainfall amounts from May to June were higher than normal in 1996 and 1998. These years showed significantly higher arbovirus activity. Deviations from normal temperature showed low correlation with arbovirus activity during the 6-year study period. Therefore, precipitation appeared to be more important than temperature in predicting arbovirus activity in Rhode Island.     

A multipurpose serological survey in Kenya. 2. Results of arbovirus serological tests

Arbovirus infections are of public health interest in East Africa, where a very widespread epidemic of o''nyong-nyong fever was reported in 1959-60 and where the threat of yellow fever, present in neighbouring areas such as Ethiopia, remains. Sera collected in a serological survey in Kenya were therefore tested for antibodies against 3 group-A arboviruses (chikungunya, o''nyong-nyong and Sindbis), 6 group-B arboviruses (Zika, yellow fever, West Nile, Banzi, Wesselsbron and dengue 1), and Bunyamwera virus. The sera were examined mainly by the haemagglutination-inhibition test but a small proportion were also subjected to virus neutralization tests.     

Arbovirus studies in Luanda, Angola. 1. Virological and serological studies during a yellow fever epidemic

A yellow fever epidemic broke out in Luanda, Angola, in January 1971 and was halted in less than 3 months by prompt mass vaccination and intensive antimosquito measures. Nine strains of yellow fever virus were isolated from hospitalized cases, but attempts to isolate the virus from Aedes aegypti mosquitos failed. A serological survey for antibodies to arboviruses in 589 sera from unvaccinated persons showed that two arboviruses were circulating in the epidemic area: the yellow fever virus and the Chikungunya virus responsible for an outbreak of dengue-like disease that occurred shortly before the yellow fever epidemic.     

我国一些地区人血清的虫媒病毒抗体调查

本文调查了28个省、市、自治区的人血清对18种虫媒病毒抗原的血凝抑制抗体,发现我国广大地区主要存在乙组虫媒病毒,但也存在甲组和布尼安病毒的可能。甲组病毒的抗体阳性数占总阳性数的16.7%(58/347),新疆、青海、黑龙江、山西、福建、甘肃省占甲组虫媒病毒抗体阳性数的84%。布尼安病毒中特别是Aino病毒的抗体阳性率较高,占总阳性数的12.7%(45/347),黑龙江8/10人阳性,其HI滴度都大于1/80,最高为1/1280,平均滴度为1/320,黑龙江、新疆、福建、北京占布尼安总阳性数的70%。乙组虫媒病毒则以乙脑为主。但其它病毒的抗体如Zika、 Kunjin的抗体阳性也很高,故推测我国除已知有乙脑、森脑、登革热外,尚有其它乙组虫媒病毒存在的可能。     

Vertical transmission of arboviruses in mosquitoes: A historical perspective

Arthropod-borne viruses (arboviruses) are mainly transmitted horizontally among vertebrate hosts by blood-feeding invertebrate vectors, but can also be transmitted vertically in the vector from an infected female to its offspring. Vertical transmission (VT) is considered a possible mechanism for the persistence of arboviruses during periods unfavorable for horizontal transmission, but the extent and epidemiological significance of this phenomenon have remained controversial. To help resolve this question, we reviewed over a century of published literature on VT to analyze historical trends of scientific investigations on experimental and natural occurrence of VT in mosquitoes. Our synthesis highlights the influence of major events of public health significance in arbovirology on the number of VT publications. Epidemiological landmarks such as emergence events have significantly stimulated VT research. Our analysis also reveals the association between the evolution of virological assays and the probability of VT detection. Increased sensitivity and higher-throughput of modern laboratory assays resulted in enhanced VT detection. In general, VT contribution to arbovirus persistence is likely modest because vertically infected mosquitoes are rarely observed in nature. Taken together, however, our results call for caution when interpreting VT studies because their conclusions are context- and method-dependent.     

Généralités sur arbovirus et arboviroses

Arbovirus diseases are mainly tropical affections caused by a heterogenic group of viruses with common epidemiological properties. About 130 known arboviruses belonging to about 12 different virus families are of human or veterinarian medical importance. Many others are not pathogenic but can be interesting models for fundamental virological studies. Arboviruses survive in nature by biological transmission between vertebrate hosts and hematophage arthropoda. Arboviruses reproduce on these without change to their life or fecundity. They are transmitted through bite or sting of infected arthropoda to receptive vertebrates inducing an early and transitional viremia. A more or less complex cycle usually follows: virus, arthropoda vector, vector, vertebrate host. According to the vector’s ecology, each arbovirus is present in a specific area and is always likely to invade a non-endemic zone. The arthropoda in question are ticks, mosquitoes, phlebotomes, or Culicoides (Ceratopogonidae). Vertebrates either spread or amplify the viremia or they are accidental hosts or epidemiological dead-ends. Three types of clinical presentations are described: febrile polyalgia (“dengue-like” syndromes); hemorrhagic fever (frequently severe evolution); meningo-encephalitis (frequently severe evolution ending by death or recovery with severe neurological sequels). Various arboviruses are responsible for the same clinical presentations; but a same virus can induce several types of syndromes which stress the importance of laboratory diagnosis, based on the virus identification and specific serological tests. Prophylaxis relies on vaccination: yellow fever, tick borne encephalitis, Japanese encephalitis and fighting against vectors. New vaccines are being studied but not on the market yet.     

海南省虫媒病毒调查研究状况

海南省地处热带北缘,自然条件适合节肢动物繁殖及虫媒病毒传播,曾发生过多次登革热大流行,也是流行性乙型脑炎(乙脑)地方性流行区.以往从海南省多种媒介和宿主动物中分离到4种甲病毒(基孔肯雅、马雅罗、盖塔和罗斯河病毒)、2种黄病毒(乙脑和登革热病毒)和1种Seadornavirus.现对海南省新分离虫媒病毒及其人畜感染状况进行回顾整理,为当地以及我国虫媒病毒病的预防控制提供依据.     

Epidemiologic History and Genetic Diversity Origins of Chikungunya and Dengue Viruses,Paraguay

Paraguay has been severely affected by emergent Zika and chikungunya viruses, and dengue virus is endemic. To learn more about the origins of genetic diversity and epidemiologic history of these viruses in Paraguay, we deployed portable sequencing technologies to strengthen genomic surveillance and determine the evolutionary and epidemic history of arthropod-borne viruses (arboviruses). Samples stored at the Paraguay National Central Laboratory were sequenced and subjected to phylogenetic analysis. Among 33 virus genomes generated, we identified 2 genotypes of chikungunya and 2 serotypes of dengue virus that circulated in Paraguay during 2014–2018; the main source of these virus lineages was estimated to be Brazil. The evolutionary history inferred by our analyses precisely matched the available travel history of the patients. The genomic surveillance approach used was valuable for describing the epidemiologic history of arboviruses and can be used to determine the origins and evolution of future arbovirus outbreaks.     

虫媒病毒及其媒介蚊虫microRNA的研究现状和展望

目前,虫媒病毒引起的严重传染病在世界范围内流行。有关虫媒病毒与媒介蚊虫间相互作用关系成为研究的热点。随着microRNA在动物、植物,甚至是病毒中的发现,使得虫媒病毒与蚊媒之间复杂的分子作用关系有了新的研究视野。本文主要综述虫媒病毒与其媒介蚊虫在microRNA水平上的相关研究进展。     

Predicting Ross River virus epidemics from regional weather data

BACKGROUND: Diseases caused by arboviruses cause extensive mortality and morbidity throughout the world. Weather directly affects the breeding, abundance, and survival of mosquitoes, the principal vector of many arboviruses. The goal of this study was to test whether climate variables could predict with high levels of accuracy (more than 70%) epidemics of one arbovirus, Ross River virus disease. METHODS: Weather data from two regions in southeastern Australia were matched with Ross River virus disease data for the period 1991 to 1999. Our aim was to develop simple models for the probability of the occurrence of an epidemic in an area in a given year. RESULTS: Two predictable epidemic patterns emerged, after either high summer rainfalls or high winter rainfalls. A prerequisite relating to host-virus dynamics was lower than average spring rainfall in the preepidemic year. The sensitivity of the model was 96% for Region 1 and 73% for Region 2. CONCLUSIONS: Early warning of weather conditions conducive to outbreaks of Ross River virus disease is possible at the regional level with a high degree of accuracy. Our models may have application as a decision tool for health authorities to use in risk-management planning.     

Yellow fever infection after recent convalescence from chikungunya fever: report of a fatal case

An epidemic of chikungunya fever occurred in Luanda, Angola, at the end of 1970, being followed by, and partly concurrent with, an epidemic of yellow fever. In March 1971, a 16-year-old white boy, who had chikungunya fever 3 weeks before, was admitted to hospital with yellow fever. He had a severe illness ending in death on the 8th day. Serum taken on admission yielded YF virus designated as strain 47FA; it is essentially identical to YF (Asibi strain) virus. This serum had HI antibody only to CHIK virus, of 11 arbovirus antigens tested. A positive CF test for CHIK antibody in this serum confirmed the earlier infection with CHIK virus. The authors speculate that persons convalescent from chikungunya fever may be less resistant to infection with YF virus.     

West nile virus disease and other arboviral diseases - United States, 2011

Arthropodborne viruses (arboviruses) are transmitted to humans primarily through the bites of infected mosquitoes and ticks. Symptomatic infections most often manifest as a systemic febrile illness and, less commonly, as neuroinvasive disease (e.g., meningitis, encephalitis, or acute flaccid paralysis). West Nile virus (WNV) is the leading cause of domestically acquired arboviral disease in the United States. However, several other arboviruses also cause seasonal outbreaks and sporadic cases. In 2011, CDC received reports of 871 cases of nationally notifiable arboviral diseases (excluding dengue); etiological agents included WNV (712 cases), La Crosse virus (LACV) (130), Powassan virus (POWV) (16), St. Louis encephalitis virus (SLEV) (six), Eastern equine encephalitis virus (EEEV) (four), and Jamestown Canyon virus (JCV) (three). Of these, 624 (72%) were classified as neuroinvasive disease, for a national incidence of 0.20 per 100,000 population. WNV and other arboviruses continue to cause focal outbreaks and severe illness in substantial numbers of persons in the United States.